The present invention relates to an arrangement on a coordinate table of a processing machine for driving a carriage movable in X-direction. More particularly, it relates to an arrangement which has a ball screw nut and a ball screw associated therewith, wherein the ball screw is supported at its ends with end supports stationary relative to the carriage.
Ball screw drives for driving in X-direction and in Y-direction are used particularly in numerically controlled coordinate tables of processing machines, particularly cutting presses. In the known coordinate tables provided with such ball screw drives, there are, however, difficulties for driving in X-direction, i.e., for driving the carriage in a direction to the tool, for the following reasons. The drive means for X-axis travel over the drive for the Y-axis in Y-direction. In numerically controlled coordinate tables, and particularly on cutting presses, the Y-axis is very often accelerated in the Y-direction and then again braked. This process can be repeated in several hundred times per minute. For stopping such movement processes in the shortest time, considerable accelerating and decelerating values are required. When the free length of the ball screw in the X-direction is particularly great, a considerable bending of the ball screw during the movement in the Y-direction takes place. Decisive for the value of this bending is the weight of the ball screw, its free length, or in other words the distance between two supports, one of which in such case is formed by a support of the nut of the ball screw drive, and the acceleration or deceleration which takes place. When the abutment of the ball screw provided for the X-direction occurs by the movement in Y-direction so fast one after the other and so that the flexure of the ball screw is not brought back to zero, a regular amplification of the vibrations of the ball screw takes place. As a result of this, the known drive arrangements for coordinate tables with great dimensions cannot be used, inasmuch as the vibrations of the ball screw which takes place exceed the acceptable value. However, for a long time there is a requirement to provide coordinate tables of great dimensions with ball screw drives, inasmuch as such ball screw drives are especially economical because the ball screws can be used both for force transmission and as a measuring system.